Centromere protein A (CENP-A) is a 17-19 kDa centromere-specific histone variant that is 62% identical to the carboxy-terminal domain of histone H3. In the presence of DNA, CENP-A forms an octameric complex with histones H4, H2A, and H2B. CENP-A defines active centromere regions by forming centromere-specific nucleosomes on which kinetochores are assembled. CENP-A is specifically located to the inner plate of the kinetochore and it is essential for kinetochore targeting of CENP-C and other kinetochore components. CENP-A is required for nucleosomal packaging of centromeric DNA at interphase.